This invention relates to lost foam patterns used in casting metal components and methods for assembling such patterns.
Lost foam patterns are generally attached to a runner which is then attached to a sprue to form a cluster of patterns. This attachment has been accomplished by hot melt adhesives, by a hot knife which welds two polystyrene surfaces together, or by solvent bonding using a material such as methylene chloride. These methods can be slow and hazardous. Further, the latter two methods do not lend themselves easily to small lot assembly. Also, highly stressed joints assembled with hot melt adhesives are prone to failure when the patterns are covered with a ceramic slurry coating and then dried quickly at elevated temperatures.
Attention is directed to the following U.S. patents which illustrate casting patterns:
______________________________________ Patentee U.S. Pat. No. Issued ______________________________________ Barishman 2,468,479 April 26, 1949 Skinner 2,508,546 May 23, 1950 Poe 3,254,379 June 7, 1966 Parsons 3,635,280 January 18, 1972 Parsons 3,707,029 December 26, 1972 Boyle et al. 3,848,654 November 19, 1974 ______________________________________
Attention is also directed to Gross U.S. Pat. No. 3,695,340, issued Oct. 3, 1972, which illustrates a polystyrene casting pattern. The pattern includes a first piece fixedly located in a reverse tapered groove in a second piece by a compressed and then restored tongue thickness sufficient to hold the tongue in the groove. The tongue is not held in the groove solely by virtue of frictional engagement between the tongue and the second piece.